The present invention relates to an improved transmission mechanism of a fax machine, and more particularly to an improved one-roller type transmission mechanism replacing a two-roller type transmission mechanism used in the conventional fax machine of the prior art.
A fax machine is capable of transmitting, receiving, and reproducing graphic matter. As shown in FIG. 1, a mechanical design of the early model of a fax machine includes two motors 10 and 11 for actuating two rollers 12 and 13 respectively. The projective reading of graphic information 14 by an optical reader 15 is driven by motor 10 and roller 12 when the fax machine is executing a transmission and reproduction of graphic information 14. Motor 11 and roller 13 are responsible for driving the heat sensitive paper 16 (the fax paper) to make contact with the printing lead 17 to print out graphic information which the fax machine has received as an incoming message. In other words, such transmission mechanism includes an information-reading portion 10, 12, and 15 and an information-reproducing portion 11, 13, and 17. These two portions are completely separated by design in order to prevent them from interfering with each other when the fax machine receives an operation signal initiating the internal control system to instruct one of the transmitting or receiving mechanisms to operate. In view of current industrial trends to add versatility to products and to miniaturize products, fax machines are nowadays made with the inclusion of an electronic device, such as memory, to broaden its peripheral application. As a result, the design of the transmission mechanisms of a fax machine, in which the reading mechanism and the reproducing mechanism are separately set up, has evolved into a more ingenious system, in which only one motor is used to actuate two rollers, as shown in FIG. 2. Such a design includes a clutch device 18, which is used to actuate rollers 12 and 13 upon receiving an operation signal. It is apparent that such a transmission mechanism with only one motor 19 is more efficient in terms of cost control and energy consumption.
This inventor is of the opinion that the information reading mechanism can be set up in combination with time information reproducing mechanism because both mechanisms make use of the rollers 12 and 13 to roll out, respectively, the graphic information paper 14 and heat sensitive paper (the fax paper) 16. However, in the process of transmitting graphic information by the fax machine, heat sensitive paper 16 must not be rolled out, and graphic information paper 14 can be easily actuated and driven by a slight force exerted upon the graphic information paper 14 located between the roller 12 and the clear view window 151, as shown in FIG. 2. On the other hand, the information reproducing mechanism is dependent on the roller 13 and the printing head 17 each of which must exert a substantial force on the heat sensitive paper 16 so as to ensure that the heat sensitive paper 16 makes good contact with the printing head 17 in order to reproduce a good copy of incoming graphic information that the fax machine has received. If we want to design a fax machine having only one roller to do all the jobs instead of two rollers 12 and 13 as described above, we must find, first of all, a way to prevent the heat sensitive paper 16 from being rolled out at a time when the process of transmitting graphic information is in progress.